The present invention relates to lubricant dispensing systems, and more particularly to lubricant dispensing systems that detect gas in a lubricant.
Excess air entrapped in grease can cause an improper amount of grease to be deposited onto production parts or in other lubricant dispensing applications. This is normally caused by incorrect grease handling, changing of the original grease container, or improper pump priming. The trapped air in grease is compressed to a relatively small volume by the grease supply pressure, which can be as high as 3000 p.s.i., but the air expands to its normal size as the grease is discharged onto the production part. The decompression of the air results in reduced amounts of grease on the production part where the grease should have been. Prior to the present invention, there was no known accurate method by which to detect and dispose of grease including unacceptable amounts of entrapped air. This problem is particularly troublesome where the charges of grease being deposited are relatively small. The lack of such an accurate method has resulted in many "faults" on parts as far as grease volume dispersion.
U.S. Pat. No. 4,993,516 to Taiani discloses an apparatus including a piston that separates a lubricant chamber and a gas chamber. If there is gas in the lubricant, the piston is moved and a relief valve is opened to allow the gas to escape through the piston and gas chamber. However, the Taiani invention does not provide an accurate way to detect a specific untolerable amount of entrapped air in the lubricant, nor does the device of Taiani provide for means to dump the charge of lubricant when the charge has the undesired amount of entrapped gas.
Other patents such as U.S. Pat. No. 3,633,612 to Gross and U.S. Pat. No. 4,520,902 to Snow teach sensing means for measuring pressure differential in a lubricant, but do not offer means for sensing undesired amounts of air in a lubricant.
Accordingly, there is a need in industry for a device that will sense undesired amounts of air in a charge of grease, and dump the charge if it contains an untolerable or undesirable amount of air. Furthermore, there is a desire in industry to be able to easily adjust the size of the charge once it is in the device that measures excess air, without discharging any of the grease first.